Gradient Rectangle in Flickable with reparented attached ScrollBars

main.qml

import QtQuick 2.12
import QtQuick.Controls 2.12

ApplicationWindow {
    visible: true
    width: 640
    height: 480

    Flickable {
        id: flickable
        clip: true
        anchors.fill: parent
        anchors.rightMargin: ScrollIndicator.vertical.width
        anchors.bottomMargin: ScrollIndicator.horizontal.height
        contentWidth: rectangle.width
        contentHeight: rectangle.height

        ScrollIndicator.horizontal: ScrollIndicator {
            parent: flickable.parent
            anchors.left: flickable.left
            anchors.right: flickable.right
            anchors.top: flickable.bottom
        }

        ScrollIndicator.vertical: ScrollIndicator {
            parent: flickable.parent
            anchors.top: flickable.top
            anchors.left: flickable.right
            anchors.bottom: flickable.bottom
        }

        Rectangle {
            id: rectangle
            width: 1000
            height: 1000
            gradient: Gradient {
                GradientStop {
                    position: 0
                    color: "navajowhite"
                }
                GradientStop {
                    position: 1
                    color: "salmon"
                }
            }
        }
    }
}